Bug#1130323: transition: python.14 as default

[Graham Inggs]

Control: block -1 by 1127773 1130893 1125251

Qt 6.10 is done, but this transition is currently blocked by abseil
(#1127773), llvm-toolchain-21, which depends on llvm-toolchain-22,
which fails its own autokgtests (#1130893) and llvm-toolchain-19,
which cannot built on s390x (#1125251).